Continuous rotary drum vacuum filter

ABSTRACT

In a continuous rotary drum vacuum filter of the type employing a filter medium in the form of an endless belt which is entrained over the drum and over rolls spaced from the drum, a device for preventing the intrusion of unfiltered slurry into filtering chambers in the drum through the clearance between the drum and the filter medium comprising a pair of endless pressure belts which press the filter medium against both sides of the drum in the portion of the drum that is immersed in a slurry tank. The pressure belts press the filter medium into channels in the edge of the drum and effect a tight seal that eliminates leakage between the filter and the drum in the immersed portion thereof.

United States Patent lnventor Altlteehi lwatani Muugame, .lapu

App]. .No. 826,412

Filed May 21, 1969 Patented Nov. 9, 1971 Assignee lshigeki Kilto Co.,Ltd.

Sahide, Japan CONTINUOUS ROTARY DRUM VACUUM FILTER 6 Claims, 7 DrawingFigs.

3.288.298 11/1966 Daughertyetal.

ABSTRACT: In a continuous rotary drum vacuum filter of the typeemploying a filter medium in the form of an endless belt which isentrained over the drum and over rolls spaced from the drum. a devicefor preventing the intrusion of unfiltered slurry into filteringchambers in the drum through the clearance between the drum and thefilter medium comprising a pair of endless pressure belts which pressthe filter medium against both sides of the drum in the portion of thedrum that is immersed in a slurry tank. The pressure belts press thefilter medium into channels in the edge of the drum and effect a tightseal that eliminates leakage between the filter and the drum in theimmersed portion thereof.

PATENTEDNUV .9 197i 3 6 l 8 7 82 SHEET 1 0F 2 4 FIG.

INVENTOR A/dzfoa/zb .ZZzlaZzZrzb ATTORNEY.)

BACKGROUND OF THE INVENTION This invention relates to an improvedcontinuous rotary drum vacuum filter of the type employing a rotary drumwith surface filtering chambers and a filter medium in the form of anendless belt which is entrained over the drum and over rolls spaced fromthe drum, and more particularly to means for preventing the intrusion ofunfiltered slurry into the filtering chambers through the clearancebetween the drum surface and the filter medium at both side ends of thedrum in the portion thereof that is immersed in a slurry tank.

A continuous rotary drum vacuum filter of the type employing a rotarydrum with surface filtering chambers and an endless belt filterentrained over the drum and over a cakedischarging roll and another rollspaced from the drum has an important advantage with respect to acontinuous rotary drum vacuum filter of the type employing a filtermedium wound on the overall surface of the drum by and secured there byadhesion in that the fcnner needs no cake-discharging cutters and thefilter medium thereof can be cleaned easily and continuously A filter ofthe fonner type, however, has a drawback due to the fact that the filtermedium is not bonded onto the surface of the drum but only runs incontact with the drum surface, the drawback being that slurry intrudesinto the filtering chambers through the clearance between the drum andthe filter medium at both side ends of the drum where it is immersed inthe slurry tank, particularly at the beginning of filteringoperation orat the cessation of filtering operation even though the said clearanceis partially sealed by the pressing of the filter medium onto thesurface of the drum due to the tension of the filter medium itself andalso by a negative pressure in the filtering chambers which is producedwhen the filter medium becomes somewhat choked by cake. Because of thisdrawback, the former filter cannot be used in filtrations in chemicalplants and the like that are required to produce highly purifiedfiltrates.

Accordingly, it is a primary object of the present invention to providea filter of the type described having a device for preventing theintrusion of slurry into the surface filtering chambers of the drumwhereby a highly purified filtrate is obtained.

SUMMARY OF THE INVENTION According to the present invention, theabove-noted object is accomplished in a filter of the type described byproviding a pair of endless pressure belts which contact on the filtermedium portion which is in the slurry tank at both side ends of the drumsurface and press the filter medium against the surface of the drum.Said pair of endless pressure belts are guided by two series of pulleysby which the belts are pressed against the filter medium in the slurrytank but not outside of the tank. In the slurry tank, the endless beltspress the filter medium onto the drum surface at both side ends of thedrum whereby the clearance between the drum surface and the filtermedium is perfectly sealed so that unfiltered slurry cannot intrude intothe drum surface filtering chambers through said clearance DESCRIPTIONOF THE DRAWINGS The present invention will become more readily apparentas the specification is considered in conjunction with the accompanyingdrawings in which:

FIG. I is a front view, partially cut away, of one embodiment of thefilter according to the present invention;

FIG. 2 is a side view, partially cut away, of the filter shown in FIG.I;

FIG. 3 is an enlarged vertical sectional view of a part of the filtershown in FIG. I seen along plane Ill-Ill of FIG. 1;

FIG. 4 is a sectional view of the filter along IV-IV of FIG.

FIG. 5 is a vertical sectional view similar to FIG. 3 but of a part ofanother embodiment of the filter according to the present invention;

FIG. 6 is a vertical sectional view of a part of the filter shown inFIG. 5 seen along plane Vl-VI of FIG. 5;

FIG. 7 is a transverse sectional view of the filter shown in FIG. 5 seenalong VII-VII of FIG. 5.

DETAILED DESCRIPTION Referring now to the drawings, in which likereference numerals designate like parts throughout the several viewsthereof, there is shown a preferred embodiment of the device accordingto the present invention in FIG. I, 2, 3, and 4. The device includes arotary drum 1 suitably mounted for rotation in a frame 2 and driven by asuitable drive mechanism, a slurry tank 3 in which the lower portion ofthe drum 1 is immersed and a filter medium 4 in the form of endless belttrained over the drum 1, a first or supporting roll 5, acake-discharging roll 6, a tension-providing roll 7 and a fourth oradjusting roll 8 for correcting the deviation of the belt 4 to aid inmaintaining proper alignment on the drum. The filter medium 4 is anetwork or sheet endless belt of a woven fabric, wire gauze and the likethrough which purified liquid can permeate and said belt 4 covers thewhole width of the surface of the drum 1. As is usual, the drum 1 isprovided with a number of filtering chambers 9 which are formed by apair of sidewalls l0 and a number of axially extending dividing walls11. Each of. the chambers 9 is subjected to vacuum applied throughconduits 12 which are connected to a filter valve 13 which operates inknown fashion to apply controlled vacuum to the drum surface filteringchambers 9 during rotation of the drum I.

As shown in FIG. 4, there are formed at both side ends of the drum apair of annular grooves 14 with generally U-shaped cross sectionsbetween the walls 10 and sidewalls of the drum by which ring packings 15of gum are received. Further, as shown in FIG. 4, there is inserted ineach of the filtering chambers 9 a plate member 16 for supporting thefilter medium 4 with a number of perforated bores 17, projections 18 onthe outer surface and feet 19 on the inner surface.

Turning once again to a consideration of FIGS. 1, 2, and 3, two pairs ofpulleys 20 and 21 are rotatably mounted onto two pair of verticalholders 22 and 23, fixed in the frame 2 at both side ends of the drum 1.Similarly, two pairs of pulleys 24 adjacent to the pulleys 20 and 25adjacent to the pulleys 21 are rotatably mounted onto two pairs ofinclined holders 26 and 27 fixed to brackets 28 and 29 respectively. Apair of endless belts 30 are trained over these two series of pulleys20, 21, 25, and 26 respectively at each side end of the drum surface.Between the pulleys 24 and 25, the belts 30 are wound on the filtermedium 4 over the ring packings IS in the slurry tank 3. Thus, theendless belts 30 run together with the filter medium 4 in the tank 3between the pulleys 24 and 25 and run at an interval apart from thefilter medium 4 and apart from the drum 1 between the other pairs of thepulleys 20 and 21. In this way, the endless belt filter medium 4 istightly pressed onto the ring packings 15 by the endless belts 30 atboth side ends of the drum 1 whereby the intrusion of slurry withoutfiltration into the filtering chambers 9 through the clearance betweenthe surface of the drum 1 and the belt 4 is perfectly prevented.

Referring to FIGS. 5, 6, and 7, there is shown another embodiment of thedevice according to the present invention. In the embodiment shown inFIGS. 5, 6, and 7, the endless belts for pressing the filter medium ontothe drum surface are trained over resiliently supported pulleys so thatsaid endless belts always run under a tension. In this improvedembodiment, a pair of pulleys 124 and 125 (pulley 125 is not shown inthe drawings) for leading the endless belt 30 on the surface of the drum1 are rotatably mounted onto holders parallel to the axis of the drum(see FIG. 6) and the other pair of pulleys I20 and 121 (pulley 121 isnot shown in the drawings) for leading the belts 30 at an interval apartfrom the filter medium 4 and the drum 1 are mounted onto a pair ofvertical holders I22 and 123 similarly to the previously describedembodiment shown in FIGS. 1, 2, 3, and 4. Contrary to said embodiment,the holders 122 for the pulleys are secured to a sliding member 31 whichis slidably inserted in a sleeve 32 fixed to the sidewall of the slurrytank 3. The member 31 has a screwreceiving bore 33 into which anadjusting screw 34 with a handle 35 at its rear end is screwed. Aroundthe adjusting member 34, there is provided a coil spring 36 between thehandle 35 and the sleeve 32. Owing to the structure mentioned in theabove, each of the pulleys 120 supported by the member 29 is supportedresiliently in the direction reverse to the other pair of pulleys 121(not shown in the drawings) so that the endless belts 30 are alwaysforced onto the surface of the drum 1 under a tension whereby tightersealings between the filter medium 4 and ring packings are achieved.

The particular advantage of the present invention consists in the factthat he instrusion of slurry into the drum surface filtering chambersthrough the clearance between the rotary drum and the filter medium atboth side ends of the drum surface is perfectly prevented no only at thebeginning of the filtering operation or at the cessation periods of thefiltering operation when slurry is left unremoved from the slurry tank,but also in the continuous filtering operation of the filter, so thatfiltrate of a very highly purified degree can be obtained.

Having now described the invention and having exemplified the manner inwhich it can be carried into practice, it will be apparent to thoseskilled in the art that innumerable variations, applications,modifications, and extensions of the basic principles involved may bemade without departing from its scope. The invention is to be limited,therefore, only by the scope of the appended claims.

What is claimed is:

1. ln a continuous rotary drum vacuum filter of the type employing arotary drum in a slurry tank, the drum having surface filtering chambersand a filter medium in the form of an endless belt trained over the drumand rolls spaced from the drum, a device for preventing the intrusion ofslurry without filtration into the filtering chambers comprising a pairof resilient rings carried by the drum at the ends thereof, the filtermedium being disposed against said rings, and endless belts wound on thefilter medium portion in the slurry tank at both side ends of the drumsurface, said belts being run together with the filter medium and beingimpressed against the filter medium in the regions of said rings to formseals at said regions between the filter medium and the rings.

2. The device according to claim 1 wherein each of the endless belts istrained respectively over four pulleys, each belt running with thefilter medium and the drum into and out of said tank between a firstpair of pulleys.

3. The device according to claim 2 wherein one of the pulleys is forleading an endless belt and is supported resiliently whereby a tensionis always provided to the belt against the filter medium.

4. The device according to claim I wherein there are formed at both sideends of the drum surface a pair of annular grooves with generallyU-shaped cross sections in which said rings are received.

5. ln a continuous rotary drum vacuum filter of the type employing arotary drum in a slurry tank, the drum having surface filtering chambersand a filter medium in the form of an endless belt trained over the druma device for preventing intrusion of slurry without filtration into thefiltering chambers comprising a pair of discrete endless belts separablefrom said filter medium and wound on the filter medium portion in theslurry tank at both side ends of the drum surface, said belts being runtogether with the filter medium and imposing pressure on the latter toseal the filter medium to the drum at the regions of imposition of saidpressure, and two series of pulleys around which each belt is trained,each belt running with the filter medium and the drum into and out ofsaid tank between a first pair of pulleys, and running apart from saidfilter medium and said drum between the other pair of pulleys.

6. The device according to claim 5 including resilient means carried bysaid drum at side end regions and against which the filter medium isimpressed by said belts.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3.6l8.782 Dated November 9 1971 Inventor s) AKITOSHI IWATANI It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 3, line 14, change "he" to -the-- Cola 3, line 17, change "no" to-not--- (301, 4, line 9, place a comma after "pulleys" and insert --andrunning apart from said filter medium and said drum between the otherpair of pul1eys.--

Signed and sealed this 11th day of July 1972.

( SEAL) Atte st:

E DWI RD N. F LET CHER JR R 05E RT GOT T SC HALK Atte sting OfficerCommiss ioner of Patents )RM PO-105O (10-69) USCOMM-DC scam-P69 Q U 5GOVERNMENT PRINTING OFFICE I969 0-355-334

1. In a continuous rotary drum vacuum filter of the type employing a rotary drum in a slurry tank, the drum having surface filtering chambers and a filter medium in the form of an endless belt trained over the drum and rolls spaced from the drum, a device for preventing the intrusion of slurry without filtration into the filtering chambers comprising a pair of resilient rings carried by the drum at the ends thereof, the filter medium being disposed against said rings, and endless belts wound on the filter medium portion in the slurry tank at both side ends of the drum surface, said belts being run together with the filter medium and being impressed against the filter medium in the regions of said rings to form seals at said regions between the filter medium and the rings.
 2. The device according to claim 1 wherein each of the endless belts is trained respectively over four pulleys, each belt running with the filter medium and the drum into and out of said tank between a first paiR of pulleys.
 3. The device according to claim 2 wherein one of the pulleys is for leading an endless belt and is supported resiliently whereby a tension is always provided to the belt against the filter medium.
 4. The device according to claim 1 wherein there are formed at both side ends of the drum surface a pair of annular grooves with generally U-shaped cross sections in which said rings are received.
 5. In a continuous rotary drum vacuum filter of the type employing a rotary drum in a slurry tank, the drum having surface filtering chambers and a filter medium in the form of an endless belt trained over the drum, a device for preventing intrusion of slurry without filtration into the filtering chambers comprising a pair of discrete endless belts separable from said filter medium and wound on the filter medium portion in the slurry tank at both side ends of the drum surface, said belts being run together with the filter medium and imposing pressure on the latter to seal the filter medium to the drum at the regions of imposition of said pressure, and two series of pulleys around which each belt is trained, each belt running with the filter medium and the drum into and out of said tank between a first pair of pulleys, and running apart from said filter medium and said drum between the other pair of pulleys.
 6. The device according to claim 5 including resilient means carried by said drum at side end regions and against which the filter medium is impressed by said belts. 